1. Technical Field
The present invention relates to machine tool rotary cutting tools in general, and to end mills in particular.
2. Background Information
A variety of end mills for use with rotating milling cutters are available and well known. Depending on design, such end mills are generally used in right hand cutting, right hand spiral and center cutting.
Some prior art end-mills have helical flutes that follow a single continuous cutting edge angle. For example, it is known in the art to form flutes at a low helix angle or a high helix angle. A “low helix” (or low helical flute) is a flute that helically “winds” around a cylinder at an angle of no more than 45 degrees. A “super” low helical flute would be a flute that winds around a cylinder at an angle of at no more than 15 degrees. A “high helix” (or high helical flute) is a flute that helically winds around a cylinder at an angle of greater than 45 degrees, while a “super” high helical flute winds around a cylinder at an angle of at least 65 degrees.
Other prior art end mills have one or more flutes with a cutting edge that continuously changes along its length. For example, prior advancements relating to material removal and feed rate of end mills have been accomplished by: (1) varying the spiral lead angle; (2) increasing the depth of the flutes in the body portion of the end mill; (3) changing the radial rake angle; (4) changing the clearance angles of the cutting edges; and (5) forming chip splitting grooves in the flutes.
While such variations have proven successful in various applications, they are also the source of certain disadvantages and limitations. For example, such variations may weaken portions of the tool and may not be suitable for particular applications (e.g., regarding milling time, rough cut, finish cut, etc.). Furthermore, existing end mills are typically not efficient for both rough cutting and finish cutting. It is often advantageous when performing an end-mill machining operation to create many small chips, rather than fewer elongated curlicue chips. This allows, for example, rapid rate of removal of material from a work piece without undue heating of the end-mill tool.
What is needed, therefore, is an end mill that has improved characteristics relative to the end mills currently available.